The death of a Twin Cities man who hit his head after being pushed during a conflict with a friend in a Minnesota casino is being treated as a homicide, authorities said Tuesday.

Donald R. McElderry Jr., 58, of Coon Rapids, was shoved on Jan. 2 at Grand Casino Hinckley and died 12 days later at North Memorial Medical Center in Robbinsdale, the Hennepin County Medical Examiner’s ruled.

The medical examiner said the killing is being investigated by the Pine County Sheriff’s Office, and charges against the suspect have yet to be filed. The Star Tribune generally does not identify suspects before they are charged.

McElderry’s girlfriend, Kathy Centolanza, saw the shove and described it Tuesday as “hard, really hard. … He saw him coming, but he didn’t have time [to react].”

McElderry, a niece, Centolanza and the suspect were at the casino, when McElderry was directed back to his room by security personnel because they felt he had enough to drink, his girlfriend said.

At some point, he came out of his room to speak with his girlfriend, and the suspect, in his 20s, “came flying around the corner” and pushed McElderry, Centolanza said.

“I was shocked when this happened,” she said, choking back sobs while recounting the incident three months later. “I watched his body go down. … I wish I could have caught him. I watched his head hit the ground.”

Centolanza ordered the suspect to call 911 “right this minute,” she said. He made the call, and the Sheriff’s Office said he’s been cooperative.

Centolanza, who had been McElderry’s girlfriend for seven years, said the suspect “has been in Donny’s life since he was a kid. But he also did take Donny away from me and others.”

Donald and Melanie McElderry were married in 2002, split up in 2011 but remained close, his ex-wife said.

She said she remembers the suspect when “he used to mow our lawn and shovel our snow.”

McElderry graduated from Blaine High School, worked taping drywall and driving big rigs, his family said.

“He helped raise all us nieces and my older daughter,” said Melinda Bucholz. “He was very involved in family.”