Thames Valley Police said officers were called by South Central Ambulance Service shortly after 01:50 GMT on Sunday. Williams, from London, suffered serious injuries in Midsummer Boulevard in Milton Keynes.
Two men, aged 21 and 28, from Luton, have been arrested on suspicion of murder, and a third man, aged 30, also from Luton, has been arrested on suspicion of assisting an offender. All three have been remanded in custody.
Detective Inspector Rob Underhill, of Thames Valley's major crime unit, said: "We recognise this incident will cause concern within the local community. There will continue to be an increased police presence in and around The Hub and Milton Keynes city centre over the coming days, and I would encourage anybody with concerns to speak with our officers."
Williams, a midfielder, joined Hendon FC in September and had previously played for Kettering Town and Marlow FC. In a statement posted to X, Hendon FC, which plays in the Isthmian League South Central Division, described Williams as a "humble, unassuming and generous individual with a razor-sharp wit". The club said he "was beginning to carve a place for himself in midfield with a series of hard-working and selfless displays that summed him up as a person".
He scored his first goal for the club 10 days ago, against Jersey Bulls. As a sign of respect, the London Senior Cup tie with Woodford Town on Wednesday was postponed.
Kettering Town FC also paid tribute to the player. A spokesperson said he had shown “great leadership qualities from the get go at his time here”. The club added: “He was a talented, kind, and a truly inspirational individual who had his faith at the forefront of his heart, and this led him to be the wonderful young man that he was, someone whose warmth touched everyone lucky enough to know him, and whose example will continue to inspire us long after today.”
Police have appealed for anyone with information, mobile phone footage, dash-cam footage or CCTV recordings from Midsummer Boulevard at the time of the incident to contact the force.