People have left flowers and piano instruction manuals outside the home of Ruthanne Lodato in Alexandria. (Jahi Chikwendiu/Washington Post)

In the days since an unknown assailant shot and killed the beloved music teacher Ruthanne Lodato when she answered her front door, a certain wariness has descended in the close-knit neighborhoods of Alexandria, where she lived her whole life.

People who have felt safe enough to leave front doors unlocked find themselves instinctively locking them. Many are scanning the faces of strangers for similarities to the sketch of the suspect — an older, balding white man with a gray beard — that Alexandria police released late Friday night.

And the ordinary act of answering a knock at the front door now comes with a touch of dread.

“Re: Knock at my door,” wrote one neighbor on a local e-mail discussion group, “If it was a neighbor who just knocked, I apologize, but I am not answering the door. Please call or send me an e-mail.”

At the Executive Lock and Key Service hardware store, locksmith Sean Harvey said he has been deluged with calls to install peepholes into front doors since Lodato’s slaying.

Composite sketch of shooting suspect (Courtesy Alexandria City Police)

“People are scared,” he said, pulling a brass peephole with a 200-degree view off the shelf. “Someone knocks on the door, you want to open it. You don’t expect someone to shoot you.”

Josh Kabler took Harvey’s business card and said he’d be calling for new locks and a peephole.

“My wife is really apprehensive,” he said. “But I just tend to think we’re so accustomed to guns in society that this is just the way it is. People get killed in car crashes. People get struck by lightning. People got shot. That’s just how it goes.”

Pam Deichmeister never gave answering the front door a second thought. But after Lodato, a 59-year-old mother of three, was killed at her front door Thursday, and after another neighbor, Ronald Kirby, 69, a director of transportation planning and father of two, was shot multiple times with an automatic weapon at his front door Nov. 11, Deichmeister says she is being cautious.

“I’m trying not to be paranoid. I think, ‘Look around, we live on a quiet street.’ Then I think, ‘But they lived on quiet streets,’ ” she said. “It just makes you feel uneasy. And watchful.”

In Alexandria, police detectives spent Saturday following leads and sifting through more than 100 e-mails that had come in since they released the composite sketch of the suspect, said Crystal Nosal, a police spokeswoman. Patrol officers were looking for anyone matching the suspect’s description, she said, and stopping people for questioning.

“We’ve been getting the word out that the sketch is not a photograph. It’s a sketch based on one person’s recollection who only caught a glimpse and was under a great amount of stress at the time,” she said “We’re telling people to remember that the suspect may have changed his appearance because this case is getting a lot of attention.”

On Saturday, as Deichmeister sat with her husband and two friends at St. Elmo’s Coffee Pub, worried talk of the unsolved killings hung over every conversation.

“It just seems so random,” said Deichmeister’s husband, Bob.

It’s not as if random violence had not already hit many close to home. As Kabler said, it’s just the way things are now.

Kabler is a graduate of Virginia Tech. His professors and people he knew were shot and killed in the massacre at the university in 2007 that left 33 dead, including the shooter, and 17 wounded.

One of Pam Deichmeister’s relatives was in a movie theater in Aurora, Colo., in 2012 when a man opened fire with an automatic weapon and killed 12 people and injured 70 others.

And Nancy Dunning, a well-liked Alexandria real estate agent, community volunteer and sheriff’s wife who was shot several times in the back in her home in 2003, was a friend. Dunning’s killing has been unsolved for more than a decade.

Bob Deichmeister remembered when another neighbor, Robert Rixse, an Alexandria doctor, was shot to death in his own doorway in 1984, a case that went unsolved for years.

Seated on a couch nearby, Steve Kronheim thought of a neighbor in Maryland killed by John Allen Muhammad and Lee Boyd Malvo in 2002 during the sniper attacks. Ten people were killed and three were wounded during the wave of shootings.

“I just feel like my perspective is changing as my sense of safety is threatened. After the shootings at the Columbia Mall a few weeks ago, I was at a Starbucks and a man came and sat next to me without ordering anything. I began to make a plan for what I’d do if he got up and started shooting. I’ve never done that before,” said Marcia Bond, sitting across from Kronheim.

“And now, after this murder, I find myself looking around, wondering, ‘Is anyone in this coffee shop carrying a gun?’ ”