Florida Murder-Suicide: Friend Tells Cops Killer Was Suicidal in Dispatch Audio

Huge update in the suspected murder-suicide down in Florida ... TMZ has obtained audio of a concerned friend asking police to do a welfare check ... and she told cops alleged killer Ryan Whiten was suicidal.

Listen to the clip -- a distraught friend of Melanie Hyer called police June 2 after she and Melanie's sister hadn't heard from her for at least a day. She says right from the get-go that Ryan has made it clear in the past he's suicidal ... which is why the friend is so worried about Melanie's well-being.

The woman even says she sent a neighbor over to the house to check in on them ... but received no answer and saw no movement despite both Melanie and Ryan's cars being in the driveway. She also notes the oven is open and a light is on, which she feels is strange.

Miami-Dade police eventually entered the home ... and found that she and her two minor daughters dead with stab wounds. Ryan was also dead in the home.

As TMZ reported, Melanie and Ryan were previously married and co-parented their daughters.