Police say the suspect linked to a shooting in Knockholt, Kent on Valentines Day "may have entered the water" at Dartford Crossing.
Police earlier confirmed that they have attended to a vehicle parked on the QE2 Bridge after a woman in her 40s was shot dead near the Three Horseshoes pub.
Senior investigating officer Detective Chief Inspector David Higham said: "Call handlers received reports of a man on the wrong side of the barrier and we are not ruling out the possibility that he may have entered the water.
"We are currently only looking for one suspect and do not believe there to be an ongoing risk to the public."
Emergency services were called to the scene at the Three Horseshoes near Sevenoaks after reports that a woman had suffered serious injuries just after 7pm yesterday.
A male suspect is believed to have fled the scene.
Police say they have started a murder investigation after the incident.
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Kent Police said in a statement: “Officers attended the scene along with South East Coast Ambulance Service where a woman in her 40s had suffered injuries consistent with gunshot wounds.
“She was declared deceased at the scene and a murder investigation is under way. Her next of kin has been informed.
“As part of inquiries, officers attended the Dartford Crossing where a vehicle linked to the incident was recovered, alongside a firearm.
“Inquiries are ongoing to identify and locate all persons potentially involved.”
Local parish councillor Ray Picot told Kent Online that he heard “a couple of loud bangs” at 7pm.
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He added: “It’s a shock. We’ve never had anything like this. It’s a very busy pub – a great pub. It never has any trouble and is very well managed.
“I understand those inside the pub were ushered back to their houses by police as they were all in terrible shock. It sounded awful.”
Another parish councillor, Steve Maines, told the BBC that he heard a “commotion” outside the venue, and was told someone had been shot.
He said: “We were sitting having our Valentine’s Day meal when all of a sudden we heard this huge commotion outside in the car park.
“We were told someone had been shot so we had to leave.”