A Florida woman has killed two of her children and critically injured the third then tried to commit suicide on Friday night, police said.

Jessica McCarty, 33, of Palm Bay, called the police just before 6pm, saying her three children were dead and she had cut her wrists.

Laci McCarty, seven, was pronounced dead at the hospital and Philip McCarty, six, died from cardiac arrest while heading for an Orlando hospital at 11.22pm. Five-month-old Christopher Swist is in critical condition at an Orlando hospital, police said.

Detectives initially said that McCarty had stabbed the children with a butcher knife, though they later retracted the statement and said it is not clear how they were injured.

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Jessica McCarty, 33, of Palm Bay, Florida, allegedly attacked her three young children, killing two and critically injuring her five-month-old son

McCarty, pictured with her partner Chris Swist, daughter Laci McCarty (right) and sons Philip McCarty (center) and Christopher Swist (in her arms), called the police on herself on Friday

Palm Bay police apprehended McCarty outside her home at about 6pm.

Officers said they had to shoot her with beanbag rounds because she was 'uncooperative' and was armed with a knife, Florida Today reported.

Police reportedly received two phone calls - one from McCarty and one from the father of the five-month-old baby, Chris Swift, who arrived home to find the children unconscious, according to WPTV.

McCarty, pictured left with partner Chris Swist and her two eldest children Laci and Philip and right again with Chris Swist, was treated for injuries and put into custody

McCarty was in the front yard when apprehended, but she 'wasn't showing her hand' after several requests to do so. She then showed she was holding a knife and refused to put it down, police said.

After refusing several requests to put down the knife, police said officers shot McCarty with five to six less-lethal 'beanbag' rounds, which are meant to subdue a person.

Police Chief Mark Renkens said that McCarty 'has a bit of a history', having been convicted of acquiring a controlled substance by fraud and violating parole in 2013 and a reckless driving charge that was reduced from a DUI in 2009.

McCarty was treated for her injuries and taken into custody, according to WFTV. Police have yet to interview her.