How do I add a knock back to a player from the entity when it's destroyed

?
PHP Code:
public fwPropaneDestroyed( entity, attacker ) {
if( !pev_valid( entity ) )
return HAM_IGNORED;
if( get_user_weapon( attacker ) == CSW_KNIFE )
return HAM_IGNORED;
static ent_t_class[ 32 ];
entity_get_string( entity, EV_SZ_classname, ent_t_class, charsmax( ent_t_class ) );
if( !equal( ent_t_class, entity_name ) )
return HAM_IGNORED;
new EntasOwner = pev( entity, pev_iuser2 );
if( !is_user_connected( EntasOwner ) )
EntasOwner = attacker;
new Float:EntasOrigin[ 3 ];
entity_get_vector( entity, EV_VEC_origin, EntasOrigin );
for( new index = 1; index <= maxPlayers; index++ ) {
if( is_user_alive( index ) && get_user_team( EntasOwner ) != get_user_team( index ) ) {
new Float:userOrigin[ 3 ];
entity_get_vector( index, EV_VEC_origin, userOrigin );
new Float:DistanceBoom = get_distance_f( EntasOrigin, userOrigin );
if( DistanceBoom <= get_pcvar_float( Entas_radius ) ) {
new victim_health = get_user_health( index );
new Float:damage_to_do = ( 1.0 - ( DistanceBoom / get_pcvar_float( Entas_radius ) ) ) * get_pcvar_float( Entas_damage );
if( victim_health <= damage_to_do && is_user_connected( EntasOwner ) )
ExecuteHamB( Ham_Killed, index, EntasOwner, 0 );
else
ExecuteHamB( Ham_TakeDamage, index, "player", EntasOwner, damage_to_do, DMG_BLAST );
// Knockback //
}
}
}
remove_entity( entity );
return HAM_IGNORED;
}