Out of the Closet
This mission involves a meeting at Brucies apartment where he explains that a guy named Tony has a hit out on him. Brucie wants Niko to meet up with Tony, and since Tony is gay, Roman is creating a profile at meet-up.net so Niko can see if Tony wants to hook up. During that date Brucie wants you to kill Tony.
You have to go to the internet cafe after that to browse to meet-up.net and find Tony's profile. Once you find it, you send him an email asking if he wants a date. Log off the computer and check back in a while and you'll find out that Tony send you an email saying he wants to hook up, and that he'll meet you at the 69th St. Diner around a set time. You have to reply to the email to get the appointment on your organizer, and to make the event happen. If you don't reply to the email, he doesn't show up.
During the day before the meetup Roman sends you various text messages telling you not to fall in love on your date, and keeps reminding you that you are going out with a guy.
Once you meet him in the diner at the arranged time (he wears a red rose so you know who he is) you sit down and start talking. At any time in the conversation you press L1 to stand up and then you can kill him however you see fit. Immediately you get a wanted level and must evade the cops to pass the mission.