https://open.mp/docs/scripting/functions/SetPlayerChatBubble
Code:
public OnPlayerWeaponShot(playerid, weaponid, hittype, hitid, Float:fX, Float:fY, Float:fZ)
{
SetPlayerChatBubble(playerid, "SHOTS FIRED", 0xFF0000FF, 50.0, 8000);
return 1;
}