A piercing sound now serves as a call for help on Winnipeg streets following a violent past two weeks.

"It's loud. It's like a cop siren or something,” said Paul Guiboche, who tested out his new personal panic alarm outside the Salvation Army’s Booth Centre on Wednesday.

A total of 300 of them were donated to the city’s three downtown shelters by National Industrial Communications after three homeless men were killed in April.

The homicides have raised fears among Winnipeg's most vulnerable citizens and the panic alarms are meant to help provide an extra level of security.

"It gives them a bit of sense that they can use this to protect themselves,” said Main Street Project Executive Director Lisa Goss.

Investigators allege a suspect killed Stony Stanley Bushie and Donald Collins within hours of each other Friday night. Their bodies were discovered less than a block apart in downtown Winnipeg.

Police also allege the suspect killed a third man on April 10. Miles Monias was fatally assaulted in a Main Street bus shelter.

Police have charged John Paul Ostamas with two counts of first-degree murder and one count of second-degree murder.

The father of the accused said he hasn't seen Ostamas in more than 10 years and only heard of the charges through a friend.

"I was surprised when I heard that someone said that John is being charged with murder," said Donald Ostamas from his home in Kasabonika, Ont.

Ontario court records obtained by CTV News paint a violent past.

Ostamas was convicted of assault in July 2002 and sentenced to 90 days in jail.

His most recent conviction for a serious offence happened in February 2012 for assault causing bodily harm. He received 12 months in jail and three months of probation.

Family members of Monias are now planning a memorial on Friday at the place where he died.

His sister Nadine Barkman said from her home in Garden Hill that she can’t think of any reason why someone would want to hurt her brother, who she described as outgoing and helpful.

“I’m just so lost without him,” said Barkman.

Homicide victim Donald Collins' family from Kenora has come forward after hearing a plea on the news Wednesday night from Winnipeg's Ma Mawi Centre for relatives to claim his body.

Collins is one of three homeless victims killed in matter of weeks in downtown Winnipeg.  Police have charged John Paul Ostamas in all three deaths.