PROVIDENCE, R.I. (AP) — With the search for the Brown University shooter in its fifth day Wednesday, authorities were asking the public to review any security or phone footage from the week before the attack in the hopes it might help investigators identify the suspect, believing he may have cased the scene ahead of time.

“We’re looking for a moment that is shorter than someone taking a breath,” Providence's police chief, Col. Oscar Perez, said at a Tuesday news conference.

The request came after authorities released several videos from the hours and minutes before and after Saturday's attack showing the suspect standing, walking and even running along streets just off campus, but always with a mask on or his head turned.

Although Brown President Christina Hull Paxson said there are 1,200 cameras on campus, the attack, which killed two students and wounded nine others, happened in a first-floor classroom in an older part of the engineering building that has “fewer, if any” cameras, Rhode Island Attorney General Peter Neronha noted. Investigators also believe the shooter entered and left the building through a door that faces a residential street bordering campus, which might explain why the cameras Brown does have didn't capture footage of him.

The lack of campus video of the shooter led President Donald Trump to accuse the Ivy League school of being unprepared, posting Wednesday on Truth Social: “Why did Brown University have so few Security Cameras? There can be no excuse for that. In the modern age, it just doesn’t get worse!!!”

Where the investigation stands

Investigators have described the suspect as about 5 feet, 8 inches (173 centimeters) tall and stocky, but they've given no indication that they are close to zeroing in him.

The attacker's motives also remain a mystery, and Neronha batted away questions about what they might be, saying Tuesday, “That is a dangerous road to go down.”

Authorities have been canvassing the surrounding neighborhoods and have received about 200 tips, and Neronha defended the investigation as going "really well" as he pleaded for patience.

But the timing of the attack, coming just before the winter break, could complicate the investigation, as remaining classes and exams were canceled after the shooting and many students have already gone home.

The investigation also comes as Boston-area police search for the person who killed a Massachusetts Institute of Technology professor earlier this week. That attack happened in the professor's home, and the FBI said it had no reason to think the two attacks were linked.

Separately, Providence police on Wednesday released a new photo of a separate individual who they said was in “proximity of the person of interest" and asked the public to help identify the person so they could speak with them. The person in the new photo is wearing dark pants and a blue jacket, and carrying a light tan bag.

Campus security comes under scrutiny

The attack and shooter’s escape have raised questions about campus security.

Paxson said Brown has two security systems. One system, activated at a time of emergency, sent out text messages, phone calls and emails that reached 20,000 people. The other features three sirens across the campus and was not activated Saturday, a decision Paxson defended because doing so would have caused people to rush into buildings, including the one where the shooting was happening.

“So that is not a system we would ever use in the case of an active shooter,” she said.

Brown's website says the sirens can be used when there is an active shooter, but Paxson said it “depends on the circumstances" and the location of the shooter.

A city on edge

With the shooter still at-large, Providence remained tense Wednesday as additional police were stationed at city schools to reassure worried parents that their kids would be safe. Some schools canceled afterschool activities and field trips.

Prior to the shooting, nearly 1,600 Providence residents were registered to receive texts through a city text alert service. According to the city, 760 new accounts have been created since Sunday, bringing the total number of people registered to receive texts to more than 2,300 as of late Tuesday.

Brown also cautioned people to refrain from accusing people online of having any link to the attack, after it said such speculation led to a student being doxed — their identifying information was posted.

“Accusations, speculation and conspiracies we’re seeing on social media and in some news reports are irresponsible, harmful, and in some cases dangerous for the safety of individuals in our community,” the school said in a statement.

Honoring the victims

About 200 people gathered at a campus church service Tuesday to honor the victims, including Ella Cook and MukhammadAziz Umurzokov, the two students who died.

Cook was a 19-year-old sophomore from Alabama who was very involved in her church and served as vice president of the Brown College Republicans.

Umurzokov was an 18-year-old freshman from Virginia whose family immigrated to the U.S. from Uzbekistan and who hoped to go to medical school one day.

Rhode Island Hospital said Wednesday that six of the seven students still at the hospital recovering from gunshot wounds are in stable condition — a noticeable improvement since only one was stable as of Tuesday. One student remains in critical condition, while two have been discharged.

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Contributing were Associated Press journalists Jennifer McDermott, Matt O'Brien and Robert F. Bukaty in Providence; Brian Slodysko in Washington; Michael Casey in Boston; Patrick Whittle in Portland, Maine; John Seewer in Toledo, Ohio; Kathy McCormack in Concord, New Hampshire; Heather Hollingsworth in Mission, Kansas; and Audrey McAvoy in Honolulu.