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Niagara Regional Police issued a Canada-wide arrest warrant on Monday for a 43-year-old man wanted for second-degree murder in connection with the death of his seven-year-old stepson.

Police said Nathan Dumas was found critically injured in a home in St. Catharines, Ont., Friday morning. He was rushed to hospital, but died early Saturday.

The stepfather, identified as Justin Kuijer, is also being sought on attempted murder charges in relation to a stabbing incident at a Royal Bank branch located at 211 Martindale Road on Friday in which a woman was sent to hospital.

WATCH: Niagara police issue Canada-wide warrant for 43-year-old Justin Kuijer. Catherine McDonald reports.

2:44 Niagara police issue Canada-wide warrant for 43-year-old Justin Kuijer Niagara police issue Canada-wide warrant for 43-year-old Justin Kuijer

Police did not immediately reveal the cause of Dumas’ death.

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“We’re not releasing that and we’re not necessarily sure people want to know that,” Const. Phil Gavin told reporters at police headquarters in Niagara Falls on Monday.

READ MORE: Man, 43, wanted for first-degree murder of stepson in St. Catharines

“It’s the death of a child. It’s a tragic situation and we’re doing everything we can to bring a resolution peacefully.”

Police said the boy’s mother, Whitney Dumas, is cooperating with the investigation.

“She’s also grieving in a terribly tragic situation at the loss of her son in a way that few people can understand and comprehend,” Gavin said. “She’s working with us. She’s got a lot of support from the community.”

WATCH: News breaks that police issue Canada-wide warrant for 43-year-old Justin Kuijer

3:26 Police to issue Canada-wide warrant for 43-year-old Justin Kuijer, wanted for first-degree murder of stepson in St. Catharines Police to issue Canada-wide warrant for 43-year-old Justin Kuijer, wanted for first-degree murder of stepson in St. Catharines

Heartbreaking obituary for 7 year old Nathan Dumas https://t.co/pDrxhHZS7p — Catherine McDonald (@cmcdonaldglobal) March 21, 2017

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In a Facebook post, Dumas said she is grateful for the support she and her family has received and asked for privacy.

“Your kind word [sic] and well wishes and down pour of donations have been truly overwhelming,” she wrote. “I understand that everyone has questions, it’s human nature, so do I! But this is truly not the appropriate time to be doing so.”

Kuijer was last seen fleeing the scene in a dark grey 2009 Pontiac Montana van with the Ontario licence plate number BYTE392.

Police said they are not investigating the incident as a robbery or a domestic violence matter but believe the woman was targeted. They also said the victim and Kuijer were known to each other professionally.

WATCH: ‘He was happy. He used to joke, play’: neighbour describes 7-year-old Nathan Dumas

1:25 ‘He was happy. He used to joke, play’: neighbour describes 7-year-old Nathan Dumas ‘He was happy. He used to joke, play’: neighbour describes 7-year-old Nathan Dumas

“It was initially reported that his actions in the bank was a failed robbery attempt or it was domestic in nature, but that’s not true,” Gavin said.

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The woman remains in hospital in stable condition.

Gavin initially said the Canada-wide warrant would be on charges of first-degree murder and attempted murder, but the charge was later downgraded to second-degree murder.

READ: 7-year-old stepson of suspect wanted for attempted murder in St. Catharines bank assault dies

Police called the suspect armed and dangerous. They said if members of the public see him, they should not approach him and call 911 immediately.

Kuijer was last seen wearing an orange hoodie under a brown leather coat, dark pants, a black toque, and boots, police said.

Authorities said the suspect’s vehicle also has a floral tribute sticker in relation to missing person “Ashley Simpson” on the rear driver’s back window.

A GoFundMe page launched on Saturday to help pay for the boy’s funeral costs has surpassed its $10,000 goal on Sunday.

Please find attached the newest wanted poster with the Canada Wide and 2nd Degree reference. Please share and get the word out. #RBCInc pic.twitter.com/u6rAzvyQPH — NRPS (@NiagRegPolice) March 20, 2017

WATCH: Niagara police issue Canada-wide warrant for 43-year-old Justin Kuijer. Catherine McDonald reports.

2:44 Niagara police issue Canada-wide warrant for 43-year-old Justin Kuijer Niagara police issue Canada-wide warrant for 43-year-old Justin Kuijer

-With files from The Canadian Press

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