Toronto police have released a video of three "persons of interest" in the death of an innocent bystander shot while hanging out with friends in a backyard earlier this week.

The men were caught on security video near 20 Driftwood Ave., in the Jane and Finch neighbourhood, where witnesses reported hearing more than 20 gunshots ring out Tuesday evening.

Four bullets struck Rachel Alleyne, a mother of three small children, while she was playing dominos and drinking beer with about a dozen other people, around 8:30 p.m., police said.

The 30-year-old was rushed to Sunnybrook hospital, but died from a gunshot wound to the upper torso.

"This murder takes the callousness of this type of shooting to a new low," Det. Sgt. Pauline Gray said at a press conference Thursday, as she displayed security images.

"The shooters walked through the complex past many, many units and several security cameras -- with apparently no worries that they would be seen."

Another woman and two men were also taken to hospital after the shooting. One man remained in critical condition on Thursday.

Investigators believe a man at the party was the intended target of the shooters.

With a report from CTV's Jim Junkin