Students are escorted from Berrendo Middle School after a shooting, Jan. 14, 2014, in Roswell, N.M. (Mark Wilson/Roswell Daily Record/AP Photo)

The 12-year-old boy accused of firing a shotgun at classmates in his New Mexico middle school this week is in many ways an atypical school shooter, according to an ABC News examination of news stories about school shootings over the past year.

At 12, the boy is the youngest person accused of a school shooting in the past 13 months. But he is unusual in other ways, too.

Academics and law enforcement agencies have yet to complete official analyses of school shootings in 2013. ABC News has compiled a list of 21 shootings from January 2013 to January 2014 in which a gunman entered a campus armed or with the goal of committing murder.

These shootings took place on campuses across the country from elementary schools to universities.

In a majority of the cases studied, attacks took place outside, in the afternoon and with a handgun.

The accused 12-year-old who injured two students at his school in Roswell, N.M., used a shotgun and launched his attack inside the building just as the school day was starting.

In all 21 cases, the shooters were males.

Here's our breakdown, BY THE NUMBERS:

WEAPON USED:

• Handgun, 9
• Shotgun, 3
• Rifle, 2
• Unknown, 7

SEX OF SHOOTER:

• Male, 100%

SCHOOL SETTING

• Elementary, 1
• Middle, 3
• High School, 9
• College, 7
• K-12, 1

Los Angeles Police Department officers along with Los Angeles County SWAT team members search the grounds of Santa Monica College near the library after multiple shootings were reported on the campus June 7, 2013 in Santa Monica, Calif. (Kevork Djansezian/Getty Images)

FATE OF SHOOTER

• Arrested, 12
• Suicide, 7
• Fled, 1
• Killed, 1

Students are escorted out of Arapahoe High School in Centennial, Colo., Dec. 13, 2013. (Craig F. Walker/The Denver Post/Getty Images)

LOCATION

• Indoors, 8
• Outside, 13

ENROLLMENT IN SCHOOL

• Current Student, 13
• Non-Student, 5
• Unknown, 3

TIME OF DAY:

• Morning, 7
• Afternoon, 9
• Evening, 5

AGES:

• 12-years-old, 1
• 15-years-old, 2
• 16-years-old, 3
• 17-years-old, 2
• 18-years-old, 2
• 19-years-old,1
• 20-years-old, 1
• 21-years-old, 3
• 22-years-old, 1
• 23-years-old, 2
• Older than 30, 3

These figures track with the FBI's findings about mass shooting incidents in general, released this month. The government found 61 percent of all active shootings involve handguns, 15 percent shotguns, 18 percent rifles and 6 percent were unknown.

ABC News' Mary Godfrey contributed to this report.