Tucson police were investigating a homicide in which a man who suffered blunt force trauma was pronounced dead Monday afternoon on the city's southeast side.

The victim was identified as Gregory Ruby, 50, said Sgt. Kimberly Bay, a Tucson Police Department spokeswoman. 

On June 26, homicide detectives worked the scene at East 22nd Street, near South Pantano Road into the evening, said Bay. 

Shortly before 3 p.m., police responded to assist Tucson Fire Department paramedics in reference to a "man down", Bay said.

The man was found on the street's northern sidewalk area by a bridge. Paramedics treated the man but he was pronounced dead at the scene, said Bay. 

Homicide detectives found out that the victim was seen with another man in the area shortly before being found unresponsive on the ground by people. Several people gave aid and performed CPR on the man, Bay said.

Detectives were interviewing witnesses late Monday night to try and determine what happened before the man was found.

Anyone who was in the area between 2 and 2:45 p.m. who witnessed any activity, or anyone who stopped to give aid is asked to call 911 or 88-CRIME, an anonymous tipster hotline.

Contact reporter Carmen Duarte at cduarte@tucson.com or 573-4104. On Twitter: @cduartestar