Officers were initially alerted to reports of a car failing to stop following a crash in Stewart Avenue at around 4.20pm today (November 11).
The woman in her 50s, a pedestrian, was treated at the scene by London Ambulance Service paramedics.
A separate incident followed nearby, with reports receiving of a man being injured by a non-police taser.
The man in his 50s was also treated by paramedics, with neither patient being taken to hospital.
Police say a suspect believed to be both the driver of the vehicle and the one who used the Taser was arrested at the scene.
He was arrested on suspicion of causing injury via road traffic collision, failure to stop, grievous bodily harm and possession of a firearm.
A spokesperson for the Met said: “Officers responded to reports of a car failing to stop following a collision in Stewart Avenue, Upminster at around 16:20hrs on Tuesday, 11 November.
“A pedestrian, a woman in her 50s, was treated at the scene by paramedics from the London Ambulance Service. In a separate incident after the collision, a man also in his 50s, was injured by a non-police taser.
“He too was treated by the London Ambulance Service. Neither him or the woman were taken to hospital.
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“A man who is believed to be both the driver of the vehicle and the one who used the Taser remains in police custody.”
Anyone with information relating to the incident is urged to contact the Met on 101, quoting 5184/11Nov.
Local residents can expected to see an increase in police presence over the coming days.
