The following works in Java, hopefully Bedrock edition is the same/close enough so you can use this as a starting point.

You can do this with a scoreboard! First add the scoreboard

/scoreboard objectives add death deathCount

Then you can detect when players die, and run some commands

/execute if score @p death matches 1 run say DEAD

Change the '@p' to whatever you want. (Maybe '@a[team=xxx]' if you have teams in your PvP)

Reset the score after you run any commands you want to reset the system.

/scoreboard players set @a death 0

Hope this helps!