Story highlights Bart Palosz, 15, shot himself with the family shotgun after his first day of school

The sophomore from Poland had endured bullying, according to a friend's mother

Friends say Bart was teased for his height -- 6-foot-3 -- and his Polish accent

A 15-year-old Connecticut boy who shot and killed himself last week with the family shotgun had sustained years of bullying, friends said Monday.

Bart Palosz committed suicide August 27 after attending the first day of his sophomore year at Greenwich High School in Greenwich, Connecticut.

Friends who knew Bart, a Polish immigrant, told CNN he was the target of bullies due to his size -- the teen was 6 feet, 3 inches tall -- and Polish accent. The friends described him as "a little awkward in his body" but said he was a "giant sweetheart" who related more with adults than his peers.

Lisa Johnson's 13-year-old son Izzy was good friends with Bart and the Palosz family. She gave one of several eulogies at his funeral Friday, saying, "Bart was one of the kindest kids I had ever met. ... It was a life-changing friendship for Izzy. Bart was two years older, and he was so kind, funny, and refreshingly different from any kid Izzy had ever been around. Our family is absolutely devastated by the loss of Bart in our lives."

"He's always been a quirky kid...really sweet but really awkward. And that's also why he and Izzy clicked so well. Even though they were different, they were similar in their manner. They were a little outside of the lines," Johnson said.

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Johnson confirmed to CNN that Bart had indeed been bullied for years and said that his family had done everything they could to inform the school district of the situation.

Kim Eves, communications director for the Greenwich School District, said the district is "looking at the entire history in his experiences in our school that is an ongoing investigation."

"He was a very quiet kid -- truly one of the nicest people I ever met in my life. I never once heard him say anything bad about anybody else. He was just kind of a really kindhearted person," said Nick Sages, 17, a senior at Palosz's school who knew him through Boy Scouts.

Johnson said that Bart did not publicly exhibit any signs of a child in trouble.

But after Bart's suicide, several posts came to light on Palosz's social network site on Google Plus that appear to reveal his internal struggles.

"Hey if I were to stab my eye out due to school caused insanity, who would miss me?" he posted in June alongside a photo of himself with a knife next to his eye.

The following month he posted, "I notice if I sound sad I'm normal and if I act happy, cheerful, and 'normal' there is a high chance that I will try to poison myself, cut myself, commit suicide, or jump in front of a truck :)"

A group of Palosz's classmates have formed a group using social media to provide peer-to-peer support anonymously for students struggling with bullying and other issues.

"Within the school students want to talk to other people who want to listen ... Greenwich High School administration has great staff and they have great social workers, but some people can't reach out to adults themselves but they can reach out to a fellow student who wants to help out," said Elias Frank, senior class vice president and one of the founders of the Facebook group encouraging students to offer each other support.

A preliminary investigation by the Greenwich Police Department found that the gun Bart used to kill himself was family owned and had been stored inside a gun locker in the home.

"The incident continues to be investigated by members of the Greenwich Police Detective Division," a police statement said, declining to provide further information.

Bart's family has flown back to Poland to bury him and was not available for comment Monday, Johnson told CNN.