Strange syntax with select

Hello,
I excuse my ignorance with SQL and my English.
I wonder if these procedures are correct or is it a bug?
I'm trying to put the result of a select within the v_saldo_ini
variable, except I realized that the postgresql created a table with
v_saldo_ini variable.

See the steps below:

CREATE TABLE contas
(
vlr_saldo_inicial numeric(14,2)) ;

select sum(vlr_saldo_inicial) as saldo_ini
into v_saldo_ini
from contas;

--postgresql created v_saldo_ini table

select * from v_saldo_ini;
saldo_ini
-----------
20000.00
(1 record)

--if I executat = ro select below, returns the table v_saldo_ini already
exists

select sum(vlr_saldo_inicial) as saldo_ini
into v_saldo_ini
from contas;

ERROR: relation "v_saldo_ini" already exists

I'm using version below PostgreSQL.

PostgreSQL 9.4.5 on x86_64-unknown-linux-gnu, compiled by gcc (Debian
4.9.2-10) 4.9.2, 64-bit

--
Edson