A 15-year-old boy is being treated for life-threatening injuries after being stabbed more than 20 times.
The teenager was attacked in Preston Gardens, Luton, at about 02:10 BST.
Det Insp Jerry Waite described the violence as “horrific” and appealed for witnesses.
“The victim received more than 20 stab wounds in this shocking incident and is now fighting for his life,” Det Insp Waite said.
“It’s absolutely vital that anyone who has any information about this incident, no matter how minor it may seem, gets in touch with us.”
One resident who lives nearby said she heard “a lot of screaming and shouting” at about 02:00.
“At first I thought it was animal screams but as they went on I realised it was a male screaming,” she said. “The screaming went on for about two or three minutes, then it all went quiet, and then the screaming started again. “It sounded like someone was in a lot of pain. It was a screaming for your life kind of scream.”