The man arrested for stabbing a three-year-old Winnipeg boy now faces a more serious charge of second-degree murder.

Dan Jensen, 33, was arrested last week and initially charged with attempted murder for the attack on Hunter Straight-Smith.

The charge has been upgraded following Hunter's death, police said Thursday. Hunter was on life-support after he was attacked early on Oct. 30. He died three days later.

Hunter's aunt Bianca Smith told CBC News she was hoping Jensen would instead be charged with premeditated, first-degree murder.

"This is not what we were expecting," Smith said in a statement late Thursday afternoon.

"The only words we can say is we are not happy and definitely not okay with this, we're all angry and shocked."

In consultation with Manitoba Justice, members of the Winnipeg police major crimes unit obtained a warrant to charge Jensen with the more serious offence.

After the attack, Hunter was on life-support for three days. He died on Nov. 2. (Submitted by family)

Police said on the night Hunter was stabbed, Jensen, who is not the boy's father, was with Hunter's mother, Clarice Smith — his on-again, off-again girlfriend — at a location on Main Street.

They got into an argument that escalated into a violent assault against Smith, according to police.

From there, Jensen walked to the home a few blocks away on Pritchard Avenue, between Salter and Charles streets, and attacked Hunter while he slept, police allege.

Officers were called around 2:30 a.m. local time on Oct. 30 and Hunter was rushed to hospital in critical condition, given two blood transfusions and put on life support.

Jensen was arrested later the same day.