1 John 3:14 says, We know that we have passed from death unto life, because we love the brethren. He that loveth not his brother abideth in death. John tells us if we can know that we have passed from death to life by loving our brother, which means all other people I believe. He adds if we don't love our brother, that death still abides in us. We cannot proclaim to have the life of Christ in us and still have hatred toward other people.
Verse fifteen adds, Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him. John then tells us that hating our brother is the same as murdering him. He then adds that no murderer can have eternal life living in him. I believe this means that anyone who is led by the Holy Spirit can never be guilty of murdering someone, and if they are a follower of Christ, they should be led by the Holy Spirit. He did not say killing someone, but murdering, or choosing to kill someone deliberately.
Verse sixteen continues, Hereby perceive we the love of God, because he laid down his life for us: and we ought to lay down our lives for the brethren. John said we can know that we love God if we are willing to lay down our life for our brothers, just as Jesus laid down His life for all people. Jesus did not just die for some people, but for all people, even those who were crucifying Him. This is the same type of love that we should have for everyone.
Verse seventeen concludes, But whoso hath this world's good, and seeth his brother have need, and shutteth up his bowels of compassion from him, how dwelleth the love of God in him? John expands this thought of not murdering our brother to leaving someone in need if we have the ability to help them. We should never put material things above showing the love of God to the world.