University of Maryland students gather for a vigil at the Memorial Chapel on campus Feb. 12 after a student shot two housemates, one fatally, then turned the gun on himself earlier in the day at their College Park home. (Jared Soares/The Washington Post)

The e-mails flooded into University of Maryland Police Chief David Mitchell’s inbox — 20 or 30 in total — with virtually the same question: “Tell me what you’re doing to keep my child safe.”

In recent weeks, parents who signed up for the school’s alert system have received five messages about robberies or attempted robberies on or near campus, punctuated by a bulletin about two indecent exposure incidents. Then a U-Md. graduate student shot two housemates, one fatally, before killing himself.

The spate of mayhem posed a problem for police and university officials, one they argue was mainly one of perception. Despite what students and their tuned-in parents think, crime at U-Md. has fallen in recent years, as it has on college campuses across the country. Some police officials blame the proliferation of systems that send out public safety alerts via e-mail, text and Twitter for fueling the false idea that universities are unsafe.

“The numbers, if you look at them, say this is one of the safest campuses in the United States,” Mitchell said. “But when you have a string of incidents, yes, fear goes up.”

Federal law has long required universities to alert their campuses of safety threats. But it wasn’t until after the April 16, 2007, massacre at Virginia Tech — a mass killing some argue could have been mitigated by a more prompt alert — that legislators and government officials injected real urgency into that requirement.

In 2011, the Department of Education published a campus security guidebook that devotes a chapter to emergency notifications. It says that “a warning should be issued as soon as the pertinent information is available.”

“This is critical; it’s expected that even if you don’t have all of the facts surrounding a criminal incident or incidents, you will issue a warning,” the book says.

Most four-year residential colleges and universities have an emergency alert system in place that sends texts and e-mails. The University of Maryland allows anyone to sign up. At Georgetown and George Washington universities, relatives receive alerts only if students add them to their accounts.

That helps explain why the more than 131,000 people who signed up for U-Md. alerts have been inundated with messages about robberies and indecent exposures in recent weeks.

Then, about 1 a.m. Tuesday, 23-year-old engineering graduate student Dayvon Green set several fires in and around the off-campus house in College Park where he lived and shot two of his roommates.

As 22-year-old English major Stephen Rane lay dead in front of the house and a wounded housemate fled to a neighbor’s, Green went around back and shot himself, police said.

Students and others took to Twitter to express their dismay. Some worried about their parents hearing the news via the text alerts.

“If my mom finds out whats been happening at umd she’s going to try to make me come home :/,” one wrote.

“The day that my mom signs up for the umd text alerts is the day that I will never go to college,” said another.

It is unclear exactly how many U-Md. parents receive the notifications. About 5,800 who signed up for alerts indicated they are a “parent,” said Maj. Marc Limansky, a U-Md. police spokesman. But the figure, he said, is low because users can get alerts without indicating their connection to the school.

Tracy Jennison of Potomac, whose son is a freshman at U-Md., said she does not subscribe to the university’s crime alerts but called her son, Alec, as soon as she heard about the shooting on the news. Jennison said that and the other incidents made her wonder, “What is going on in College Park?”

“I am sure that every parent feels the way I do,” she said. “I worry about it every day.”

Experts say officials need to strike a balance — not over- or under-using their alert systems.

“When a text alert comes across to a student’s cellphone, they need to take action immediately,” perhaps avoiding campus or locking the dorm door, said S. Daniel Carter, who works for a campus safety advocacy group started by the families of victims and survivors of the Virginia Tech massacre. “If they get an alert about a situation that has already been resolved, they’re going to take it less seriously.”

That students will heed police warnings, after all, is not a given. When a gunman fled toward Ohio University after a robbery last month, officials canceled classes. But instead of holing up inside, some students went to the bars, tweeting about their revelry using the hashtags #FugitiveFest and #GundayFunday, according to reports in the student-run newspaper.

Georgetown Police Chief Jay Gruber said he believes that is one “unintended consequence” of a well-intentioned law.

“I would say that most colleges struggle with the same thing,” he said.

Of the five recently reported robberies at Maryland, only one was on campus — a Feb. 8 incident in a parking lot in the heart of campus. Another robbery was determined to be a story fabricated by a student who owed a relative money. Police made arrests in two of the other cases.

Crime at Maryland has fallen in many categories in recent years. There were five robberies last year, including two off-campus cases in which U-Md. police arrested suspects. In 2005, there were 18 robberies. Overall crime on campus dropped by nearly 5 percent from 2011 to 2012, according to university police data.

And while some people believe crime has risen in the immediate off-campus area, crime rates have remained relatively flat there, according to data from Prince George’s County police.

Mitchell said he sent a letter to the campus community Thursday highlighting some of his force’s recent efforts to keep the campus safe, including beefed-up patrols. He said the university has allocated $500,000 to hire and equip five new officers to patrol off-campus areas — including the neighborhood where the shooting took place.

Mitchell said he plans to send out a similar message monthly that discusses crime on and off campus and efforts to stop it. That, he hoped, might put the worried parents who e-mailed him at ease.

“You would infer from those alerts that this huge crime wave is coming through campus,” he said. “There needs to be, though, a balance here where we look at a bigger picture.”

Jennifer Jenkins contributed to this report.