The score was level at 1-1 just before the hour mark when the Hatters defender collapsed with nobody close to him.
Luton boss Rob Edwards ran onto the pitch as players were ushered away, with some in distress at what had just happened.
Referee Simon Hooper paused play and both teams made their way to the touchline as Lockyer received extended medical treatment from paramedics before leaving the pitch on a stretcher.
Luton have now confirmed the 29-year-old is stable in hospital and undergoing further tests.
The club posted the following update on X, formerly know as Twitter: "Our medical staff have confirmed that the Hatters captain suffered cardiac arrest on the pitch, but was responsive by the time he was taken off on the stretcher.
READ MORE ON PREMIER LEAGUE
Man City suffer title blow as Palace stage comeback to delight Arsenal and Liverpool fans
Chelsea end painful 15-month streak as Cole Palmer shines against Sheffield United
"He received further treatment inside the stadium, for which we once again thank the medical teams from both sides.
"Tom was transferred to hospital, where we can reassure supporters that he is stable and currently undergoing further tests with his family at his bedside.
"We would like to thank everyone for their support, concern and loving messages for Locks."
The match was suspended in the 65th minute, with a tannoy message at the Vitality Stadium saying players and managers would decide if the game will resume.
Most read in Football
Newcastle's nightmare injury crisis gets worse as two stars limp off against Fulham
Delia Smith's car hit by lager can as Ipswich fans stage hostile welcome for Norwich
'Amazing' Ange Postecoglou tipped to succeed Pep Guardiola at Man City
VAR overrules Yves Bissouma booking as Tottenham star is sent off for serious foul play
After a lengthy delay, the match was called off, as both Bournemouth and Luton emerged from the dressing rooms to applaud the fans, with Hatters boss Edwards visibly emotional.
Lockyer previously collapsed during the Championship play-off final in May before making a full recovery.
An earlier statement from Luton read: "We are sorry to all supporters present that players from both sides were in no state of mind to continue with the game after seeing their much-loved team-mate and friend taken off like that, and staff could not carry on with managing the game in such circumstances having had to deal with the situation.
"We thank everyone for the wonderful applause and singing of Locks' name inside the stadium at such a difficult time.
"Now is the time for all of our players, staff and supporters to come together as we always do and give our love and support to Tom and his family.
"Our thoughts are with him and them all."
Reporting on the game for talkSPORT, ex-Arsenal winger Perry Groves said: "I don't think there's any way at all psychologically you could come out and play a game of football.
"You could see Bournemouth manager Andoni Iraola going over to Rob Edwards and saying, 'We won't play the game', as far as he was concerned."