A man has been killed in a frenzied attack in front of diners at a busy Sydney restaurant, allegedly stabbed by the ex-partner of the woman he was taking on their first date.

Horrified patrons fled in terror from the Kang Nam BBQ restaurant in the Hornsby Westfield Shopping Centre as Keith Collins and Jovi Pilapil were stabbed repeatedly while eating dinner on Wednesday night.

Alexander Villaluna, 44, is charged with murder and attempted murder over the killing of Mr Collins and the injuries suffered by Ms Pilapil.

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Ms Pilapil, 38, is recovering in Royal North Shore Hospital after undergoing surgery.

She had taken out an apprehended violence order against Villaluna less than two months ago.

Mr Collins’ daughter Aisling took to social media on Thursday afternoon to mourn the 53-year-old’s death.

“I love you more than anything dad, I’ll forever be your girl no matter what,” Aisling Collins wrote.

Mr Collins’ profile features a large picture of a Dr Seuss quote: “don’t cry because it’s over, smile because it happened” and many selfies of him with a broad grin.

It lists his hometown as Dublin but shows he was living at Terrigal, on the Central Coast.

On Wednesday, Mr Collins had travelled south to Hornsby for his first date with Ms Pilapil.

But instead of sharing a meal the couple were attacked.

Ms Pilapil was stabbed in the chest and on the arm during the attack, which was witnessed by scores of terrified diners.

One has said Mr Collins “dropped” after being stabbed twice in the neck and a further two times in the stomach with a glass bottle.

“It was an argument because the guy cheated on his missus for him. The guy was like ‘well, you had my missus’,” one witness told the Nine Network.

Following the brutal attack, Villaluna allegedly sat covered in blood beside a fountain and waited about five minutes for police.

Footage of his arrest shows an officer pointing a Taser at Villaluna, ordering him to drop his backpack and kneel on the ground before being handcuffed.

Detective Acting Superintendent Damian Henry wouldn’t confirm whether a knife or broken bottle was used, but said a number of items had been taken from the scene for forensic examination.

Villaluna made no application for bail during a brief appearance before Hornsby Local Court late on Thursday and will remain behind bars until his case returns to court on May 26.

Meanwhile, friends have praised another witness for his bravery.

He grabbed a tyre lever and followed the alleged attacker between the restaurant and the fountain, in case anyone else was targeted.

Michael Short, who claimed the man was carrying a “massive hunting knife”, criticised Westfield security who he said didn’t arrive at the scene until after police, despite being in the area moments before the attack.

“Not saying they had to arrest him or stop him but someone had been stabbed. No first aid kit. Nothing,” he said.

A Westfield spokeswoman told AAP she couldn’t comment on the specific security arrangements but said the security team was working with police.

-with Toby Mann, AAP