Mum's chilling email revealed after she blew her children up

A concerned dad whose children were blown away by their mother desperately told police his ex-wife was going to harm the children, new 911 tapes have revealed.

West Palm Beach police have released 911 tapes of Florida father Richard Berman's desperate attempts to tell them he and another family member received an email from ex-wife Jennifer Allen.

"My ex-wife said she was going to harm the kids and that I should get over there ASAP," Berman told a 911 operator on Monday morning after Jennifer sent the chilling email.

"She sent me an email that she did the best thing for our family and then she sent her cousin a text that she was going to kill the kids and herself."

Berman told the 911 dispatcher that his ex-wife had one of her dad's old rifles.

By the time police reached the residence, the 48-year-old mother-of-two had already gunned down her 16-year-old son, Alex, and her 15-year-old daughter, Jacqueline.

She then turned the gun on herself.

Police say they are still trying to piece together all of the details of the apparent murder-suicide.

"What we have to be cautious of is not to rush to judgment as to how they died. And that is why we wait for the medical examiner," said West Palm Beach Police spokesman David Lefont.

Friends say Jennifer Allen had recently become unsettled under the pressure of her work and divorce.

"Going through a divorce, foreclosure, a lot of that stuff which, it's an upsetting thing," a family friend told news station WSVN.

"When you're going through a divorce and having to sell the beautiful house in this neighbourhood, and it's just she just seemed like she had been upset lately."

Family and friends say they'll remember Alex as an accomplished cello player and his sister Jacqueline as a straight-A student.

"This came as a giant shock," said family friend Jay Kaufman.

"We are trying to cope with the shock right now. Family and friends are beside ourselves. We did not see this coming and this is one of those things that hits you like lightning."