The court document states:

"At 8:27:24, the defendant removed his knee from Mr. Floyd’s neck. An ambulance and emergency medical personnel arrived, the officers placed Mr. Floyd on a gurney, and the ambulance left the scene. Mr. Floyd was pronounced dead at Hennepin County Medical Center.".

So it seems they took the blood on his way to the hospital or right after they arrived but before he was declared dead.

The court document states:

"At 8:27:24, the defendant removed his knee from Mr. Floyd’s neck. An ambulance and emergency medical personnel arrived, the officers placed Mr. Floyd on a gurney, and the ambulance left the scene. Mr. Floyd was pronounced dead at Hennepin County Medical Center.".

So it seems they took the blood on his way to the hospital or right after they arrived.

Yes. Weird.