Murder suspect James Allen knew one of his alleged victims, police said today.
Cleveland Police said Allen lived next door to Colin Dunford in Middlesbrough.
The 35-year-old suspect is being urgently sought by police following the separate murders of Julie Davison, 50, in Whitby, North Yorkshire, and 81-year-old Mr Dunford.
At a press conference today Chief Superintendent Gordon Lang confirmed Allen was on court bail for an offence which was not disclosed.
He confirmed Allen had also had contact with the probation services and was being investigated for other alleged offences which he would also not disclose.
He said Allen had previous convictions for violence and was a known drug user.
The detective said there had been a number of reported sightings in Middlesbrough, Scarborough and Whitby.
He also urged the suspect to give himself up saying: "James Allen stop now. Do the right thing.
"Consider the consequences.
"You have inflicted terrible injuries and death on two families.
"Stop and hand yourself in."
Mr Lang said: "People should take common sense precautions, safety first. Lock their doors, lock their windows and check who's knocking on your door.
"Clearly this is a man who is a dangerous man but we are putting absolutely everything into finding him, tracking him down and bringing him to justice.
"There's a massive police operation in place here. Over 100 detectives, two forces, not an inch between these two forces, absolutely working in partnership with one goal and that is to find James Allen and arrest him.
"I would appeal to general members of the public. If you've got an elderly neighbour then look out for them, reassure them. Be public spirited, be community spirited and help them."
Cleveland Police and North Yorkshire Police issued a joint appeal to find Allen after officers linked the two deaths yesterday.
A post-mortem examination on Mr Dunford, who was last seen alive at around 5pm on Sunday, showed he had suffered serious head injuries as a result of a significant assault.
He was found dead at his terrace house in Leven Street, Middlesbrough, on Monday after he failed to appear at the Samuelsons Working Mans Club, where he was a daily visitor.
Detectives said there was no sign of forced entry at the house.
Ms Davison, who lived alone, was found dead by her sister at her rented flat in Church Square. She had also suffered serious head injuries, police said.
North Yorkshire Police said they wanted a man with a dark-coloured mountain bike to come forward after he was seen near the flats at around 6.30am on Wednesday.
Detectives described the killings as "two brutal murders in the victims' own homes".
Cleveland Police earlier confirmed that a number of officers were involved in an "ongoing operation" on a housing estate in the Pallister Park area of Middlesbrough as part of the huge effort to find Allen.
Police stood guard outside a property in Lothian Road in Middlesbrough today as forensic officers in white boiler suits entered the property.
Neighbours said Allen was seen at the property at the weekend.
Adeel Baig said he last saw Allen at about 5pm or 6pm on Sunday evening as the suspect got into a taxi.
He said: "He was a normal bloke. Always polite. I thought he was trying to sort his life out."
He said he also saw him on Saturday with a baby who Allen said was his granddaughter.
"I was surprised. I thought it was his daughter. She was only about six months old.
"After that I saw him on Sunday as he walked towards a taxi. On the Sunday he had knocked on my door and asked to borrow some pots and pans."
Mr Baig said armed police flooded the street today.
"I had dropped my daughter off at school and arrived back at about 9.05. I was still in the car.
"Six or seven police vehicles arrived and officers got out with their weapons and ran to the house. They asked me to go to the bottom of the road. They were walking towards the house with guns."
Mr Baig said an elderly man in the house came out of the property with his hands up and was taken away by officers. He said the man had lived at the property for about 20 years.
Mohammed Salim Afsar, who lives opposite the raided house, said he saw Allen about four days ago.
"He was walking down the road quickly towards a taxi. He said he was a bricklayer and asked if I wanted any work doing.
"He said he was going to Scarborough. I recognised his photo and rang the police yesterday. I saw him, I recognised his picture."
Allen is known to police and members of the public are urged not to approach him but to dial 999.
He is described as 5ft 7in, with a bald head and tattoos on both arms.
The detective said he was also investigating an alleged offence at Allen's address in Lothian Road over the weekend, but officers had not been able to speak to him about it.
Mr Lang said Allen, who was originally from Blackpool, knew Mr Dunford when he lived next door to him in Leven Street about a year ago.
The officer said it was not thought Allen knew Ms Davison.
He said robbery was a possible motive behind the attacks, but he stressed he was keeping an "open mind" and was focusing on apprehending Allen as soon as possible.
Police said it was possible Allen could have tricked his way into Ms Davison's home.
Officers are keen to trace a black pedal bike with suspension which Allen had with him.
Mr Lang said it was feasible Allen had cycled between Middlesbrough and Whitby - a distance of more than 30 miles (48km) - although the officer said they were also looking at other modes of transport that he may have used.
The bike was seen outside Ms Davison's home and at Mr Dunford's property.
He described Allen's possible state of mind as "confused and chaotic".
He added: "We are 100 per cent committed to tracking him down. This is a 24/7 operation. If you see James Allen, do not confront him, dial 999."