Baton Rouge - Just days before he was shot and killed on Sunday morning, a Baton Rouge police officer posted an emotional Facebook message saying he was "physically and emotionally" tired and expressing how difficult it was to be both a police officer and a black man, a friend said on Sunday."I swear to God I love this city but I wonder if this city loves me," Montrell Jackson wrote.Friends and family of Jackson, 32, were mourning the 10-year-veteran of the police force that relatives described as a "gentle giant" and a "protector" after he and another two law enforcement officers were shot and killed on Sunday morning by a gunman.Sgt. Don Coppola Jr. of the Baton Rouge Police Department identified the other slain Baton Rouge police officer as 41-year-old Matthew Gerald, who had been with the department less than a year.The third officer killed was 45-year-old sheriff's deputy Brad Garafola, a 24-year veteran, spokeswoman Casey Rayborn Hicks for the East Baton Rouge Parish Sheriff's Office said.'Please don't let hate infect your heart'In the Facebook posting Jackson said while in uniform he gets nasty looks and out of uniform some consider him a threat."I've experienced so much in my short life and these last 3 days have tested me to the core," the posting read.The message was posted July 8, just three days after a black man was shot and killed by police in Baton Rouge. That shooting was the beginning of an extremely tense week in the country's fraught history of race relations. Another black man was shot and killed by police the next day in Minnesota, with his girlfriend livestreaming the aftermath on Facebook. Then a black gunman opened fire during a protest against the police shootings in Dallas, killing five police officers.Jackson does not specifically refer to those events but the posting appears to be a reaction to them.Erika Green told The Associated Press on Sunday that she is friends with the family of Jackson, one of three Baton Rouge law enforcement officers who were killed on Sunday morning. She said she saw the message on his Facebook page.In the message, Jackson says he is physically and emotionally tired."These are trying times. Please don't let hate infect your heart," Jackson wrote.A screenshot of the image has been widely circulating on the internet but is no longer on Jackson's Facebook page.Jackson's family was mourning the officer Sunday afternoon.'Gentle giant'Kedrick Pitts, the 24-year-old younger half brother of Montrell Jackson, said he was very close to his older brother."With him it was God, family and the police force," Pitts said outside his mother's house in Baton Rouge, where family was gathered Sunday. "He went above and beyond ... He was a protector."He said his brother had been on the force for 10 years, having joined in 2006 and had risen to the rank of corporal.Pitts said he woke up on Sunday to find his mother crying as news broke about the shooting involving police. He drove his mother to the hospital and it was there that they discovered that Jackson had been shot. He said Jackson leaves behind a wife and a 4-month-old son named Mason.Jackson and his family were planning to go to Houston soon for a vacation, Pitts said.Pitts, stunned by his brother's death, put on a brave face and did not shed any tears. "I did all the crying I can do. It's not going to bring him back," he said.Pitts described Jackson as a person with a humorous streak but a serious side. He said he was fond of shoes and had a collection of more than 500 pairs - such as special Kobe Bryant and Michael Jordan shoes. He said his brother was a big fan of the New Orleans Pelicans and the Dallas Cowboys.He called Jackson a hard-working police officer who often worked seven days a week.His aunt, Octavia Lacey, a 55-year-old disabled woman in Baton Rouge, called Jackson an exceptional person."Never a problem (as a child,)" she recalled. "Good spirited child."She expressed disbelief that her nephew was shot by someone who allegedly came from out of state. "I don't get it," she said.In the rural Livingston Parish, family of Jackson's wife was also mourning their loss.Lonnie Jordan, Jackson's father-in-law, spoke to reporters on the front lawn of Jackson's house. Jordan said he heard about Jackson's death while at church on Sunday morning when he received a text message.Jordan described his son-in-law as a "gentle giant" - tall and stout and formidable looking, but with a peaceful disposition, saying he was "always about peace."Jordan said his son-in-law had been working long hours since the death of Alton Sterling and the resulting protests. But Jordan said if the work was a strain, Jackson didn't let it show.