Two people have been hospitalised and another man is dead following a dramatic string of carjackings around southern Sydney on Friday.

Police said the incident started when a 24-year-old man from Greenacre with "mental health issues" engaged in a car chase with officers at Bass Hill.

The man, who was known to police, then stole a small supermarket delivery truck at Chullora and drove to Rockdale, having "a number of crashes" en route.

7News

Members of the public attempted to intervene, resulting in the 24-year-old stabbing a man in his early 20s. The victim is currently in St George Hospital in a serious but stable condition.

In a video shared on social media, the offender was then seen carjacking a taxi before he does a U-turn, mounts the curb, briefly drives along the footpath and then speeds away on the wrong side of the road.

Police eventually stopped the man at Arncliffe, before he turned the knife on himself.

"My understanding is that police have confronted him, attempted to utilise the taser, but prior to police using any of their actions, he has then stabbed himself," Acting Assistant Commissioner Mick Fitzgerald told reporters.

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Police said there is no indication the matter is terror-related.

"The offender wasn't trying to intentionally harm people. Obviously, he did hurt people, but he could have, if he wished to, harmed a great deal of both humans and vehicles if he wished to," Acting Assistant Commissioner Fitzgerald said.

"This was a man who was attempting to do everything he could to avoid arrest. His actions, in particular the actions when he stabbed the innocent person, were the actions of a person who we believe had mental health problems."

A critical incident team will now investigate all circumstances surrounding the incident.

AAP

A witness, who asked not to be identified, was working at a business on West Botany Street when people in shock were brought into the building.

The witness told AAP that police and other onlookers told her a truck had run into cars before the driver carjacked a red taxi and fled.

A Woolworths truck remains parked on West Botany Road. Woolworths has been contacted for comment.

Readers seeking support can contact Lifeline on 13 11 14.