An investigation into the fatal stabbing of two boys with “their whole lives in front of them” has gathered pace as police said they had arrested two more men in connection with the killings. Max Dixon, 16, and Mason Rist, 15, were attacked by a group at about 11.20pm on Saturday in Knowle West, a neighbourhood in south Bristol. They died later in hospital. Avon and Somerset police on Monday said two men, aged 20 and 22, had been detained, while two others, a 44-year-old man and a 15-year-old boy, had been arrested previously. All four remain in custody. There was much speculation among the shocked community in Knowle West as to the motive behind the killing. Bristol commander, Supt Mark Runacres, would not comment when asked if Max and Mason were the intended victims of the attack but appeared to rule out gang involvement. Speaking on the corner of Ilminster Avenue and Newquay Road in front of floral tributes left for the boys, Runacres said: “Bristol is a large city. And it’s described by many as a city made up of many villages. So there are people who have pride in the neighbourhoods that they come from and that’s part of their identity. But I don’t believe that this is rooted in a gang war.” Max and Mason are understood to have been friends and both attended the Oasis Academy John Williams secondary school, a mile from the scene. A friend of Dixon’s, Mitchell Lyth, 22, was working at nearby Filwood Community Centre on Saturday night and saw the police helicopter above the streets around the time of the stabbing. He said he had known Dixon since he was a baby and had seen him earlier in the evening at about 7pm. “He was a very quiet kid, very respectful. You would never ever think of him being in this sort of situation. He was always on his PlayStation 4.” “He would never be a target, he would never get mixed up with anyone,” he said. “He’s never been in trouble.” In a tribute on Facebook, Mason’s sister, Kayleigh, said: “My baby brother … one of a kind you are. You sleep tight. A beautiful, kind soul gone. Just taken 16 years so young and innocent oh my heart is broken. “I really hope you know how much we love you. How much I love you. You will be missed kiddo I’ll always look out for you in every sunset, shine bright lil’ bro.” On Monday, a regular community meeting at the Eagle House youth centre, about 100 metres from the scene, was full with residents concerned about the stabbings. Police officers attended to reassure the community. But many exiting the meeting expressed their concern and anxieties about antisocial behaviour, gang violence and knife violence in the area. Knowle West has a population of about 12,000 and is one of the most economically deprived neighbourhoods in the city, with a third of its working-age residents described as economically inactive. Jonathan Gill, who owns the nearby Premier convenience store on Newquay Road, near the scene of the killings, said: “This area has a big problem with antisocial behaviour. If you look up the number of complaints, there must have been so many of them. All we hear from the police is: ‘We’re doing our best’. “On a weekday, you’ll see 30 or 40 kids up and down the road. Residents are afraid to come out in the street. Our street is not safe at all, this has been going on for six or seven years. It’s a red alert area. Old people are scared to come to the shop at night-time because of the gangs there.” Tributes were placed near the scene including flowers and cards. A letter had been taped to the fence behind, addressed to Mason from his “Mum, brother and sister”, paying tribute and appealing for information. “Mason you are the best thing that happened to our family and we miss you so much it hurts. We can’t cope without you and can’t wait to see you again. You are so strong and brave.” It added: “If anyone has information please we beg, inform police, until the people have been caught we can’t get justice.” Runacres said more than 100 police officers were working on the investigation with support from neighbouring police forces. He said: “Any death is awful, but the loss of Mason and Max, who had their whole lives in front of them, is particularly tragic and my heart breaks for the families who have to endure such unimaginable pain and suffering. Our thoughts remain with them during this time.”