The devastated family of a two-year-old boy apparently killed by his father in a murder-suicide have described their “incomprehensible grief” at the loss.

The body of toddler Rowan was found alongside his father, 38-year-old James Harrison, in an East Lismore unit on Sunday.

Authorities have said Harrison was on an access visit with the two-year-old. The boy’s mother, Sophie Roome, contacted police on Sunday when her son was not returned by 4.30pm, as expected.

Several hours later, officers discovered the two bodies in a house in the northern New South Wales town.

“A more tragic event you wouldn’t come across … it’s very sad and that’s a matter now being investigated and a report will be prepared for the coroner,” NSW Police Deputy Commissioner Peter Thurtell said.

On Wednesday, Roome and her family spoke about the loss of their “beloved Rowan”, describing him as a “beautiful” and “joyful” little boy.

“He had so many amazing qualities, and his short life was filled with rich and happy experiences,” their statement to the ABC said.

“He loved music, the beach, swimming, his friends and his family.

“He touched the hearts of everyone lucky enough to be in his world.”

The family said Rowan’s death was “an evil and cowardly act of violence, perpetrated by a person he should have been able to trust the most”.

“There are no possible excuses for this hurt, and no end to the pain it has caused,” they wrote.

“We are devastated … We will love and miss Rowan forever.”

The family also acknowledged “the suffering of James’s family, which is also immense”.

According to reports, Rowan lived with his mother but had scheduled access visits with his father. Harrison was the subject of an Apprehended Domestic Violence Order taken out by Roome almost a year ago.

Thurtell said Harrison was known to police for previous domestic violence matters but there had been no “significant issues”.

NSW Premier Chris Minns said his government would act immediately on any recommendations the coroner might make following an investigation into the twin deaths.

“It’s completely heartbreaking. I can only imagine what that mum’s going through today. It’s an evil act, just an evil act. I’m horrified by it and I’m sure the community is completely in despair about it,” he said in nearby Cudgen on Wednesday morning.

The deaths of Harrison and Rowan followed a four-day blitz across NSW that led to more than 550 people being charged with 1070 offences.

Of those arrested, 226 were wanted by police for serious domestic violence offences.

Senior police said such statewide operations were just one way they were tackling the state’s domestic violence crisis.

They pointed to the regular execution of search and arrest warrants, the “Empower You” mobile app that lets victims record evidence with authorities and incoming legislation criminalising coercive control as part of a multifaceted approach.

“It’s really important for us that we’ve got a suite of tools because … offenders change their behaviour, not only with victims, but with the law as well,” Thurtell said.

“The more legislation, the more ability we have to interact with domestic violence offenders, the more opportunity we’ve got to change their behaviour or put them in jail.”

The blitz included 3735 domestic violence order checks and another 1300 bail compliance checks.

Thurtell said domestic violence offences were rising, but it showed people were increasingly willing to come forward.

“Once the coercive control legislation comes into play on July 1 and victims start to understand what it is … that may see an increase yet again,” he said.

The NSW government is set to tweak bail laws to keep high-risk domestic violence locked up or electronically monitored.

The presumption that high-risk offenders can be released on bail will also be reversed, with the onus of proof instead on accused perpetrators to demonstrate why they should be out in the community.

The changes follow a series of serious attacks on women. The include the death of Molly Ticehurst, allegedly at the hands of a former partner previously been accused of raping and stalking her.

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-with AAP