Attacking another player uses 25 energy every time the option is chosen. To attack, go to someone's profile and click the word Attack. The next screen will show a list of equipped weapons, the gun's ammo and remaining clips, and any guns needed to be reload. The list includes the primary weapon, the secondary weapon and whatever melee weapon is equipped. Under certain circumstances, fists are also an option.
When you use a weapon by clicking it once (twice will send you to the hospital), you will see the result. If neither you nor your opponent has lost, you will repeat the sequence until one of you loses or you each take 25 rounds.
1. You tried to hit (name) but missed (600)
2. Using his Glock 18, <name withheld> fired 5 rounds at you, doing 518 damage (82)
It will look similar to this. In this case, the attacker used a melee weapon and missed, while the defender used a Glock 18 gun and did 518 damage. Your remaining HP is in blue, while your opponent's remaining HP is in red.
You can also have critical hits and random hits, depending on the weapon. Critical hits will double or triple your base damage, potentially doing a lot of damage, while a random hit will allow you to hit even if you normally cannot.
If you win, you will be given three options. You can leave them, mug them, or hospitalize them. Leaving them gives you level experience, mugging them gives you minimal level experience and a percentage of their cash, and hospitalizing them increases their time in the hospital approximately sixfold and your forfeit you experience. If you lose or run and get shot, you will be sent to the hospital for a certain amount of time and 50 energy used. If you run and do not get shot, you will not be sent to the hospital though 50 energy will still be used. If you use up the 50 round during battle and tie with your opponent, no energy is used.