(NewsNation) — A Milwaukee man has been charged in the death of a special education teacher who was beaten and strangled near a bus stop on the city’s north side last week.

The teacher, Harry Bruce, died at the scene.

Daylan Mallar, 22, faces one count of first-degree intentional homicide, according to a criminal complaint filed Monday in Milwaukee County court. A conviction carries a life sentence.

Witness: Victim told her to ‘go’ as he was attacked

A woman getting off a city bus told police she saw a younger man overpowering an older man in a grassy area just north of the shelter. She identified the younger man as Mallard and said he held Bruce in a headlock and punched him in the head 20 to 30 times while Bruce bled from his nose and mouth, unable to defend himself.

The woman told police Mallard threatened to come after her next. She told him she was calling 911. She said Bruce, gasping for air, told her to “go,” according to the complaint.

While she was on the phone with 911, the woman said she saw Mallard drag Bruce by a key lanyard wrapped around his neck. She said Bruce was crying and begging for help until his legs stopped moving. She told police Mallard kept hitting him after he went limp, then began forcefully pulling on his head with both hands.

Three men who were waiting for food at a nearby restaurant told police a woman ran up to them, yelling that someone was being killed. They followed her and found Mallard pulling up on the lanyard around Bruce’s neck while pushing down with his foot. They yelled at him to stop, and one of the men pulled the lanyard away. One of the men told police Mallard came toward them and was pushed back. Another said he started CPR on Bruce.

Officers arrived to find Mallard pacing near the bus stop in only his underwear and socks, according to the complaint. He was taken into custody.

Security video from a nearby apartment building shows a person punching another person on the ground for around three minutes, according to the complaint. The video shows the attacker starting to walk away, then running back and attacking again.

Church: Victim was helping someone else before attack

Police have not said what led to the attack. The woman told police someone at the scene said Bruce had been waiting at the bus stop when a man charged him “for no reason.”

A news release from Bruce’s church said Bruce “was attempting to help a woman who was reportedly being assaulted when he was attacked,” according to reporting from Fox 6 Now, though the criminal complaint does not describe a previous assault.

The Milwaukee County medical examiner found that Bruce died from repeated blows to the head and neck and from being strangled by hand. His injuries included broken bones in his neck and throat and bleeding around his brain.

Victim was special ed teacher, football coach, author

Bruce taught special education at a local middle school for 13 years, where he was also a football coach, tutor and mentor to many students, according to a letter from the school’s principal.

“He made a lasting impact on the lives of those he worked with, and his presence will be deeply missed throughout our school community,” Roosevelt Middle School of the Arts Principal Tiffany Fisher wrote in the letter. “He was always a positive force. I remember him working so hard just to be a better person. And that was a model for all of us.”

Bruce was also an author who published a 110-page collection of poems and short stories dealing with marriage, addiction, illness, death and everyday struggles, written over 23 years. His family said he wrote it to offer uplifting, practical messages to help readers through their own hard times.