The boyfriend of a 36-year-old woman gunned down on the doorstep of her neighbour’s east Hamilton home has been arrested in what police are calling a “domestic-related homicide.”

Natasha Thompson, a mother of two daughters 16 and 11, was pronounced dead en route to hospital Monday night after being shot multiple times at a Lang Street CityHousing Hamilton townhouse complex around 5:15 p.m., said Homicide Unit Det. Sgt. Peter Thom.

Police allege Mark Joseph Champagne, 41, initially ran from the scene, crossing through backyards, but later turned himself in to Toronto Police Service’s 41 Division without incident around 4:30 a.m. Tuesday.

Read more: Neighbours describe hearing brazen shooting that left one woman dead in Hamilton

The pair was heard arguing inside their townhouse unit 15 before the shooting. It’s alleged that argument spilled outside and Thompson was shot on a neighbouring doorstep at unit 17.

“The argument started in their own residence, she left and the argument continued outside,” Thom said.

Police believe a handgun was used, but no weapon has been recovered.

Thompson’s 16-year-old daughter was inside the home and heard the argument and gunshots, but did not witness the murder, Thom said. Her 11-year-old daughter was not home at the time.

Both girls are with family, he added.

Champagne is “known to police” but not for domestic violence against Thompson, Thom said.

A flood of condolence messages have been posted on social media, where many remembered Thompson as a loving person and dedicated mother to two daughters.

Thompson’s former partner and the father to her younger daughters was Phonesay (Pun) Chanthachack who was fatally shot by Hamilton police in 2012. She was outspoken in her call for answers in his death, repeatedly speaking with the Spectator about her loss and how she believed police failed her family.

Detectives believe Thompson and Champagne had been in a relationship since April and were living together.

Police were executing search warrants at both Lang Street townhouse units Monday, with the possibility of expanding to a ground search for the murder weapon.

It’s alleged Champagne fled westbound on Lang Street, then north on Reid Avenue North. He cut across Lewis Street, before last been spotted near the Ukrainian Catholic church on Melvin Avenue.

Anyone with information or who may have security footage in the area are asked to contact police.

Champagne was described by police as a 41-year-old man, who is not white, about 200 pounds, six-foot, with black hair that is shorter on the side and longer on the top. He often wears removable gold grills in his front teeth.

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After turning himself into Toronto police, Hamilton police transported him back to central station in Hamilton, where he was interviewed, before being transferred to court to be formally charged. He was expected to briefly appear in court Tuesday.

Anyone with information is asked to contact Homicide Unit Det. Ross Johnson at 905-546-3827.

To provide information anonymously call Crime Stoppers at 1-800-222-8477.