UPDATE: Just to note references to M79 bullet is based on a translation of what Suthep states in Thai. Ask him why he calls them M79 bullets and not M79 grenades.

Washington Post:

The Italian ambassador, Michelangelo Pipin, raised the death of Fabio Polenghi, an Italian photographer, in the clashes Wednesday, asking that Thailand “bring those responsible to justice.” Suthep, the deputy prime minister, said the Italian had “died side by side” with a Thai soldier when both were struck by an M-79 grenade of the type used by protesters.

But as with most of what occurred Wednesday, the circumstances of Polenghi’s death are far from clear. The Italians are looking into another allegation: that he was killed not by a protester’s grenade but by a bullet, which hit him while he was running from a line of Thai soldiers.

Tried to find a version in Thai, but most of them don’t cover what Suthep said to the Italian Ambassador. The only thing I could find was from Matichon which quotes Suthep as thanking the Italian Ambassador for the support and having confidence in the Thai government (ด้านนายสุเทพกล่าวตอบว่า ขอขอบคุณเอกอัครราชทูตอิตาลีที่ให้กำลังใจและให้ความเชื่อมั่นในรัฐบาล), but at the same time he expressed his condolences for the death of an Italian journalist (แต่ขณะเดียวกันต้องแสดงความเสียใจที่ผู้สื่อข่าวอิตาลีต้องมาเสียชีวิต). He was certain though that the envoy followed the news and have probably seen the images that it only took one M79 bullet to cause the solider(s) and the death of the Italian journalist who were side-by-side ตนเชื่อว่าทูตได้ติดตามข่าวสารจากสื่อมวลชน และคงเห็นภาพชัดเจนว่าด้วยกระสุนเอ็ม 79 นัดเดียวกันได้ทำให้ทหารไทยกับผู้สื่อข่าวอิตาลีเสียชีวิตเคียงข้างกันเลย).

NOTE: Just found a Krungthep Turakit article which also refers to Suthep saying a M79 bullet killed him while he was side-by-side with soldiers.

BP: Okay, now you are thinking so? Well, all other reports were that he was shot in the stomach which implies a bullet and he was located on the red side. The Bangkok Post:

Some 50 other media friends, mostly photojournalists, showed up to say goodbye to Polenghi, a 48-year-old freelance photographer and documentary maker, who was shot in the stomach while covering the Army move to disperse red-shirt protesters in central Bangkok last Wednesday morning.

Asianews (Italy):

Of the five victims there is also an Italian photojournalist Fabio Polenghi, 45, shot in the abdomen and chest by bullets fired during clashes between the army and demonstrators

International Federation of Journalists:

The Milan-based freelance photojournalist was shot in the stomach and died in hospital. He had been wearing a bullet-proof vest and a helmet when he was shot, hospital sources said.

AP:

The family of Italian freelance photographer Fabio Polenghi say he was killed by gunfire during clashes between the military and demonstrators in Bangkok.

Italian news reports said Polenghi, 45, had been in Thailand for three months on assignment for a European magazine, whose name wasn’t immediately given. Italian journalists in Bangkok said he was wearing a bulletproof vest and helmet when shot in the stomach Wednesday. They said he was rushed by motorscooter to a hospital, where he died.

These photos here, here, and here (the last one it is particularly) seem to incidcate a small hole in his chest – a high quality shot of one of the images is image 33 here.

Matichon also states he was shot in the chest (ถูกยิงเข้าที่หน้าอกจนเสียชีวิต) – the Thai Government’s Fact Report excerpts this on this page.

The clincher is really this Thai Rath report which states a representative of the Italian Embassy came to collect the body of Fabio and the doctor explained that result of the autopsy was that a gun bullet entered the heart, causing damage to the lungs, liver, and a great los of blood. The bullet was a high velocity bullet (ตัวแทนสถานทูตอิตาลี มาติดต่อขอรับศพ นายฟาบิโอ โปเลงกี (Mr.Fabio Polenghi) ช่างภาพอิสระชาวอิตาเลียน ซึ่งเสียชีวิตจากเหตุการณ์จราจลในพื้นที่กรุงเทพมหานคร บริเวณสวนลุมพินี เมื่อวันที่19 พ.ค. ที่ผ่านมา ทั้งนี้แพทย์ได้อธิบายผลการชันสูตรศพว่า บาดแผลกระสุนปืนทะลุขั้วหัวใจ ทำลายปอด ตับ เสียโลหิตเป็นปริมาณมาก ลักษณะของกระสุนมาจากมุมสูง). Nation Channel reports similiarly.

The Der Spiegel reporter who knew Fabio and was with him earlier in the day and it is clear he was not side-by-side with soldiers, but was on the red side. Key excerpts:

When we looked for Adun [BP: a red shirt] the next day, he was nowhere to be found. Chaos was everywhere. Fabio and I saw the smoke, and the soldiers behind it, advancing towards us — and we heard an increasing number of shots. Snipers from a side street were targeting us.

The onslaught had begun. I didn’t dare go any farther, but Fabio ran forward, across the street, where shots were regularly fired — a distance of roughly 50 meters (160 ft.) — and sought shelter in a deserted Red Cross tent. This marked the beginning of the no man’s land between us and the advancing troops. I saw his light blue helmet marked “press” bob into view. He waved for me to come join him, but it was too dangerous for me up there.
…
At 11:53 a.m. I tried to reach Fabio by phone. His voicemail clicked in, which wasn’t unusual. You could only occasionally get a signal. Across from the temple, in front of the police hospital, a number of journalists were waiting for the paramedics to arrive with the wounded. A nurse noted the admissions on a board. It was 12:07 p.m., and she had already written down 14 names. A foreign reporter stood next to me. He said that they had shot an Italian. Right in the heart. Over one and a half hours ago. He said that he had taken his picture. He even knew his name: Fabio Polenghi.

BP: Suthep refers to one M79 bullet killing Polenghi and from the wording that soldier(s) died as well. Well, a single bullet doesn’t kill multiple people. It is clear from all the other reports and even from the autopsy report, he was shot by a gun bullet. Was Suthep trying to mislead the foreign diplomats, he mispoke, or he simply confused Fabio with Chandler, the Canadian journalist who was injured when he was side-by-side with the soldiers? Neither of these three possibilities is particularly comforting because you hope that before he spoke Suthep knew what he was talking about.