Police are appealing for an 18-year-old wanted in connection with the murder of a father-of-one to come forward.
Kevin Johnson was father to seven-month-old Chase
Kevin Johnson, 22, was stabbed during an argument with a group of youths outside his home in Partick Road, Sunderland, early on Saturday.
Two boys, aged 16 and 17, have been arrested on suspicion of murder.
A third, who is still believed to be in the area, is being sought. Police are not releasing his name but say family and friends are aware he is wanted.
Detectives also want to trace anyone in the Pennywell or Grindon area who may have had items of clothing stolen from their washing lines between midnight and 0900 BST on Saturday.
The attack on Mr Johnson is being linked with a series of other early hour incidents involving three youths, including another stabbing.
A spokesman for Northumbria Police said Mr Johnson left a 26-year-old partner, who is not being named, and his seven-month-old son called Chase.
"Kevin's family want to thank everyone who has come forward to the police so far and are urging anyone else with information to come forward for his sake," said the spokesman.
Police were called to Partick Road at 0025 BST on Saturday. Two minutes later there were reports of three youths causing damage in nearby Geddes Street.
At 0030 BST police were told of an attack on another man in his 20s, who was stabbed in the chest in Galway Square. His injuries are not believed to be life-threatening.
There was another report of three youths causing damage at a Shell garage in Broadway one-and-half-hours later.
SATURDAY MORNING ATTACKS
0025 BST Kevin Johnson stabbed in Partick Road
0027 BST Disturbance in Geddes Street
0030 BST Man stabbed in Galway Square
0203 BST Shell garage damaged in Broadway
Det Ch Insp Roger Ford, who is leading the investigation, said anyone who heard anything during these incidents should contact police.
"We now believe there are strong links between the four incidents," he said.
Mr Johnson's death follows two stabbing deaths earlier this month in the Northumbria force area.
Shane Jackson, 15, died in Newcastle-upon-Tyne earlier this week and 16-year-old Mark Smith was murdered on 3 May, also in Newcastle.
However, Northumbria Police said its area was a safe place to live and work and there was not a knife culture.
Sunderland area commander Supt Kay Blyth said most attacks involved people who knew one another.
"We understand people's concern about knife crime when they hear about incidents such as these over recent weeks but I want to stress the region remains a safe place to live and work.
"There isn't a knife culture in Northumbria. Of the nine murders in the force area last year involving knives, almost all of them happened in private houses."