An independent commission investigating a mass shooting that left 18 dead in the US state of Maine issued an interim report on Friday that has found that a sheriff’s office had cause to take the killer into custody and take his guns from him beforehand.

Democratic Governor Janet Mills and attorney general Aaron Frey assembled the commission to review both the events leading up to October 25, when army reservist Robert Card killed 18 people in a bowling alley and a bar, and the response to the tragedy.

Led by a former chief justice of Maine’s highest court, the commission also included a former US attorney and the former chief forensic psychologist for the state.

It held seven sessions starting in November, hearing from law enforcement, survivors and victims’ family members and members of the US Army Reserve as it explored whether anything could have been done to prevent the tragedy and what changes should be made.

Card, who was found dead from a self-inflicted gunshot after a two-day search, was well known to police, and his family and fellow service members had raised flags about his behaviour, deteriorating mental health and potential for violence before the shootings.

In May, relatives warned police that Card had grown paranoid, and they expressed concern about his access to guns.

In July, Card was hospitalised in a psychiatric unit for two weeks after shoving a fellow reservist and locking himself in a motel room.

In August, the US army barred him from handling weapons while on duty and declared him nondeployable. And in September, a fellow reservist texted an army supervisor about his growing concerns about Card, saying: “I believe he’s going to snap and do a mass shooting.”

But law enforcement officials told commission members that Maine’s yellow flag law makes it difficult to remove guns from potentially dangerous people.

“I couldn’t get him to the door. I can’t make him open the door,” said Sgt Aaron Skolfield, who visited Card’s home for a welfare check in September.

“If I had kicked in the door, that would’ve been a violation of the law.”

In later evidence, those involved in the search for Card in the shooting’s aftermath acknowledged potential missed opportunities to find him and end the search that locked down the community and terrified residents.

Some of the most emotional testimony came family members who tearfully described scenes of blood, chaos and panic followed by unfathomable loss.

Rachael Sloat, who was engaged to be married to shooting victim Peton Berwer Ross, told the committee that her heart breaks every time their two-year-old daughter asks for her daddy.

“Where are you?” she said. “Every politician, every member of law enforcement, every registered voter in the country – I want you to hear those words ‘Where are you?’ Because, my fellow Americans, where are you? We failed my little girl.”