If the guy was high going in after him was a major risk.
But no one had a float to throw him?
A rope?
A grab pole?
And fifteen minutes? That is a bit long to try to come up with a plan.
Do police have flotation equipment in every police car, on the off chance that someone jumps in a river or lake?
I don’t know the answer to that, but pose the question, as to whether police can anticipate every stupid thing somebody might do.
Of course if the guy was high on drugs, he may well have drowned anyway, even if police did have flotation devices on hand.
We need more information to know what our judgement should be.
Cop cars generally don't come equipped with floats, ropes or grab bars.
As for jumping in to save the junkie, no fully clothed cop in their duty uniform is going to jump in a river to save a guy being pursued. That's suicide.......